Simple or isolated microphthalmos is an eye shorter than the mean by two standard deviations (typically<21.0 mm) with a normal anterior chamber depth and scleral thickness and no anatomical malformations.
Cataract surgery in short eyes is surgically challenging with a higher risk of intra- and postoperative complications. In addition to the increased risk of uveal effusions, an increased risk of aqueous misdirection, cystoid macular edema, choroidal haemorrhage, vitreous haemorrhage, retinal detachment and corneal decompensation has been described. The eye is situated deeper in the orbit and often has poorer pupil dilation and the closer proximity of the iris to the cornea increases the risk of Descemet's flaps, iris prolapse into the surgical wound and intraoperative corneal endothelial damage.
This study by Yosar et al evaluated the visual outcomes and complications of phacoemulsification surgery in adult short eyes and nanophthalmic eyes at a single tertiary hospital. The secondary purpose was to compare the predicted postoperative refraction in these patients.
The records of all patients with axial length <21.0 mm undergoing phacoemulsification with intraocular lens implantation at an adult teaching hospital were retrospectively reviewed. The main outcome measures were corrected distance visual acuity and refraction at 90 days after surgery and intra- and postoperative complications occurring during the followup period.
A total of 71 eyes of 51 patients were included. Surgery resulted in an improvement in corrected distance visual acuity in 53 eyes (74.6%) (95% confidence interval, logMAR 0.11–0.29) and was logMAR 0.30 or better in 47 eyes (66.2%).
Worsening of corrected distance visual acuity occurred in 9 eyes (12.7%). Median postoperative refractive error was −0.75 dioptres. SRK/T and Kane formula were more accurate in predicting postoperative refraction than Barrett Universal II and Hoffer Q when based on mean absolute error (P < 0.005).
Complications occurred in 18 eyes (25.4%). The most frequent complications were iris prolapse, Descemet's membrane and/or endothelial trauma, transient severe corneal edema and cystoid macular edema. There was no statistically significant difference in complication rates between senior surgeons and senior trainees (P = 0.66).
This study evaluates the outcomes and complications of cataract surgery in adult short and nanophthalmic eyes using modern surgical techniques. It confirms that cataract surgery in this population is associated with a higher complication rate than in normal-length eyes but is safer than first reported.
The limitations of this study were the relatively short follow-up period of three months as well as theretrospective design. A longer follow-up period would be useful in assessing whether the reduction in IOP following surgery results in a reduced need for glaucoma medication in nanophthalmic glaucomatous eyes. Future studies may also evaluate the efficacy of pre-phacoemulsification procedures to deepen the anterior chamber (such as anterior vitrectomy) to prevent common complications such as iris prolapse and Descemet's membrane trauma.
The majority of cases resulted in improved vision and were uncomplicated. Study results supported recent studies that cataract surgery in short eyes including nanophthalmic eyes is safer than first reported. Challenges in short eye and nanophthalmic cataract surgery remain: complication rates are higher than in non-nanophthalmic eyes, and postoperative refraction is much more difficult to predict, even with the availability of multiple and new IOL formulae.
Source: Yosar et al; Clinical Ophthalmology 2021:15 4543–4551
https://doi.org/10.2147/OPTH.S344465
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